This study focuses on the teaching language used by real university instructors in the classroom.Using a corpus analy-sis approach,the article transcribes over 40000 words of teaching recordings to observe the use of language by university teachers in the context of actual communication situations.It summarizes the language characteristics of university teachers during lectures under the constraints of six principles of politeness,and analyzes the strategies they use in language usage.Suggestions are provided for fur-ther improving teaching language skills and educational effectiveness,such as using specific praise and agreement,employing inter-personal interactive speech markers,conducting reasonable turn-taking in conversations,using implicit and tactful sentence struc-tures,and effectively summarizing and generalizing student viewpoints.The application of politeness principles can make it easier for students to accept new knowledge and the teacher's perspectives,promote the development of teacher-student relationships,and en-hance the teacher's language with more affinity and persuasiveness.